In this photo made with a fish-eye wide-angle lens, "Bertha," the massive tunnel boring machine, is shown ready to begin drilling in July 2013 in Seattle.

In this photo made with a fish-eye wide-angle lens, "Bertha," the massive tunnel boring machine, is shown ready to begin drilling in July 2013 in Seattle.

Photo: Ted S. Warren, AP

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The boring machine had cleared about 370 feet of tunnel when this state Department of Transportation photo was taken on Oct. 24, 2013.

The boring machine had cleared about 370 feet of tunnel when this state Department of Transportation photo was taken on Oct. 24, 2013.

Photo: Multiple

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Bertha's Twitter account posted this photo on Dec. 6, 2013, reporting that the tunneling machine had passed the 1,000-foot mark.

Bertha's Twitter account posted this photo on Dec. 6, 2013, reporting that the tunneling machine had passed the 1,000-foot mark.

Photo: Washington State Department Of Transportation

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A drill rig is prepared to dig along the Alaskan Way Viaduct after Bertha hit an underground obstruction.

A drill rig is prepared to dig along the Alaskan Way Viaduct after Bertha hit an underground obstruction.

Photo: Joshua Trujillo/seattlepi.com

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Concrete sections that will line the Seattle waterfront tunnel are shown during a media tour on Friday, January, 24, 2014.

Concrete sections that will line the Seattle waterfront tunnel are shown during a media tour on Friday, January, 24, 2014.

Photo: JOSHUA TRUJILLO, SEATTLEPI.COM

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The approach to the Seattle waterfront tunnel is shown under construction during a media tour on Friday, January, 24, 2014.

The approach to the Seattle waterfront tunnel is shown under construction during a media tour on Friday, January, 24, 2014.

Photo: JOSHUA TRUJILLO, SEATTLEPI.COM

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Workers ride in a crane basket in the launch pit for the tunnel boring machine "Bertha" on Friday, January, 24, 2014.

Workers ride in a crane basket in the launch pit for the tunnel boring machine "Bertha" on Friday, January, 24, 2014.

Photo: JOSHUA TRUJILLO, SEATTLEPI.COM

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The Seattle waterfront tunnel and the rear of the tunnel boring machine "Bertha" are shown during a media tour on Friday, January, 24, 2014.

The Seattle waterfront tunnel and the rear of the tunnel boring machine "Bertha" are shown during a media tour on Friday, January, 24, 2014.

Photo: JOSHUA TRUJILLO, SEATTLEPI.COM

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People look over the construction site of the Seattle waterfront tunnel from the Alaskan Way Viaduct during a media tour on Friday, January, 24, 2014.

People look over the construction site of the Seattle waterfront tunnel from the Alaskan Way Viaduct during a media tour on Friday, January, 24, 2014.

Photo: JOSHUA TRUJILLO, SEATTLEPI.COM

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A worker walks in an area that will house the SR 99 approach into the tunnel on Friday, January, 24, 2014.

A worker walks in an area that will house the SR 99 approach into the tunnel on Friday, January, 24, 2014.

Photo: JOSHUA TRUJILLO, SEATTLEPI.COM

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The construction zone for the approach to the Seattle waterfront tunnel is shown under construction during a media tour on Friday, January, 24, 2014.

The construction zone for the approach to the Seattle waterfront tunnel is shown under construction during a media tour on Friday, January, 24, 2014.

Photo: JOSHUA TRUJILLO, SEATTLEPI.COM

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The construction site of the Seattle waterfront tunnel is shown during a media tour on Friday, January, 24, 2014.

The construction site of the Seattle waterfront tunnel is shown during a media tour on Friday, January, 24, 2014.

Photo: JOSHUA TRUJILLO, SEATTLEPI.COM

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The south connection between the State Route 99 tunnel and a new portion of the highway is shown near completion. The pavement and walls are exactly what drivers will see when the tunnel opens. Drivers will get in the left lane (roughly where the ladder is) to exit to Royal Brougham Way, the stadiums, Sodo and Pioneer Square. less

The south connection between the State Route 99 tunnel and a new portion of the highway is shown near completion. The pavement and walls are exactly what drivers will see when the tunnel opens. Drivers will get ... more

Photo: Washington State Department Of Transportation

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Crews continue work on the State Route 99 tunnel’s south portal operations building in April 2014. The west wall of the pit (center of this image) is where crews will make a large hole to connect the basement of the future building to the adjacent tunnel launch pit, connecting the operations building’s four large ventilation stacks to the tunnel and providing an access point for maintenance workers. less

Crews continue work on the State Route 99 tunnel’s south portal operations building in April 2014. The west wall of the pit (center of this image) is where crews will make a large hole to connect the basement ... more

Photo: Washington State Department Of Transportation

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Construction at the north portal of the State Route 99 tunnel is shown looking south in early March 2014. The site is about three blocks northeast of the Space Needle at the north edge of Downtown Seattle.

Construction at the north portal of the State Route 99 tunnel is shown looking south in early March 2014. The site is about three blocks northeast of the Space Needle at the north edge of Downtown Seattle.

Photo: Washington State Department Of Transportation

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Reinforced concrete segments that will be connected to form the outer walls of the State Route 99 tunnel sit in the storage yard of the EnCon casting facility in Frederickson, Wash.

Reinforced concrete segments that will be connected to form the outer walls of the State Route 99 tunnel sit in the storage yard of the EnCon casting facility in Frederickson, Wash.

Photo: Washington State Department Of Transportation

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A couple blocks east of the Space Needle crews have completed excavation of the 85 foot-deep pit where Bertha will complete its 1.7 mile-long journey under Downtown Seattle.

A couple blocks east of the Space Needle crews have completed excavation of the 85 foot-deep pit where Bertha will complete its 1.7 mile-long journey under Downtown Seattle.

Photo: Washington State Department Of Transportation

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State: Bertha to get back to work by next March

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Bertha, the tunneling machine that's supposed to be digging its way under the Downtown Seattle waterfront, will start moving again by the end of March 2015, the state announced Monday.

The new State Route 99 tunnel is now scheduled to open in November 2016.

Bertha stopped moving in December, after hitting an obstruction about one-tenth of the way into the 1.7-mile dig, which is the centerpiece of the $3.1 billion project to replace the aging, earthquake-damaged Alaskan Way Viaduct. The machine is the world's largest tunnel borer, with a 57.5-foot diameter.

Under a schedule that contractor Seattle Tunnel Partners released Monday, the company will start building a pit late next month to access Bertha and repair damage. The company plans to remove the machine's cutter head and start repairing damage to the seal system and main bearing in October, test the machine in February and then resume digging.

This would delay tunnel boring by up to 16 months, but the contractor hopes to recover up to four months of schedule and open the tunnel in November 2016. That was the state's original planned opening date, although Seattle Tunnel Partners had originally proposed opening the tunnel in late 2015.

"Resuming tunneling will take longer than any of us would have liked, but making these repairs is a significant engineering challenge that must be done safely," Chris Dixon, Seattle Tunnel Partners project manager, said in a news release. "We are committed to this project, and to taking the necessary steps to recover time and open the tunnel to drivers by WSDOT's original target date."

Todd Trepanier, Alaskan Way Viaduct program administrator for WSDOT, said: "We are disappointed by this delay, but we believe the new schedule is moving in the right direction. We'll continue to work with STP in their efforts to resume tunneling."

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Trepanier added that more than $750 million worth of work at the tunnel portals and elsewhere along the State Route 99 corridor "continues full speed ahead." This work includes the future connection between the tunnel a new highway section west of the stadiums and a connection between the tunnel and Aurora Avenue North, north and south portal operations buildings and the 80-foot-deep pit where the Bertha will emerge once it's done digging. Over in Frederickson, workers have made 72 percent of the concrete segments that will be pieced together to form the tunnel's exterior walls.